To clarify the pudendal motor nerve(PMN)play in preventing fecal incontinence(FI)after low anterior resection(LAR) for lower rectal cancer, the PMN function was studied at early postoperative period after LAR. A total of 30 patients aged 43 to 78 years (21 men and 9 women with a mean age of 62.4 years) who underwent LAR for LRC were enrolled in the present study. Based on postoperative FI, these patients were divided into 2 groups(group A: patients with FI[n=10], group B: patients without FI[continence, n=20]). These were compared with group C(n=28, control subjects, 18 men and 10 women aged 46 to 76 years with a mean age of 60.2 years). Magnetic stimulation at the S2-4 sacral levels has been shown to activate the PMN root of the cauda equina. PMN latency(PMNL)at posterior sides of the anal canal was studied. FI after LAR was also evaluated by the Wexner score(WS). All patients were pathological Stage Ⅰ(20 patients: T1, N0, M0; 10 patients: T2, N0, M0). Group A had a significantly larger proportion of men than group B(p<0.05). The distance of anastomosis from anal verge(DAAV)in group A(2.4±1.7 cm)was significantly shorter than in group B(4.4±0.9 cm)(p< 0.001). WS from 8 to 10(mean: 9.25)comprised 20.0% of group A, 11 to 15(mean: 13.5)50.0%, and 16 to 20(mean: 18.5)comprised 30.0%. All patients in group A(WS: 8 or more)were incontinent. In contrast, all patients in group B(WS: 0)and C(WS: 0)were continent. Patients in pre-operative defecation(WS: 0)were also continent. As for PMNL, the conduction delay in group A(7.9±0.9 ms)was significantly longer than in groups B(4.1±0.6 ms)and C(3.9±0.3 ms) (p<0.001, respectively). FI after LAR with a short DAAV may be EAS dysfunction due to damage of PMN.